1. Field of the Invention
Machines for making or forming beads on steel drums by inserting expandable dies in each end of the drum and removing same after the bead is formed, sometimes known as bead forming machines or just beaders.
2. Description of Prior Machines and Methods
The No. 812 bead expander produced by Atlanta Grotnes Machine Company of 300 Selig Drive, S. W., Atlanta, Ga., 30336, may be characterized as primarily a mechanical apparatus for forming the beads or rolling hoops into a steel drum. The machine is a horizontal type which means that the heads with the expanding dies for forming the bead traveling in and out of the open end of the drum positioned between the opposed heads. The drive mechanism for each head comprises a large gear at a respective end of the machine which is operated through a series of beveled gears and a common drive shaft by means of an air clutch. Each gear has a pin located off-center from the central axis of the gear which pin is a crank pin or pivot for a connecting rod and which is located at the other end of the head. Each drawbar operates a cone which is used to expand the dies for beading. Each head must be stopped in its travel into the drum when the position of the bead die is correct in its location from the end of the drum. This is accomplished by stop rods which physically restrain the head from moving forward any further during the stroke of the drawbar. The drawbar not having reached a full stroke position continues forward and when the head stops the drawbar travels into the bead die expanding it into the drum and forming the bead. The further the drawbar moves into the dies the higher the bead will be. The drawbar comes to a stop in its forward motion and begins to retract as the gear continues to rotate. The cone is retracted out of the dies first and then the head itself is retracted by the drawbar. The cycle is completed when the head is totally out of the drum body and in its extreme return or back position. At this time the clutch is deenergized and a brake is applied. There is quite a lot of mechanical shock each time a bead is formed.
The No. 203 bead expander produced by Atlanta Grotnes Machine Company may be characterized essentially or primarily as an all hydraulic beader. In the place of the mechanical drive, drawbar and crank system mentioned previously in connection with the No. 812 bead expander, the No. 203 bead expander utilizes hydraulic cylinders which stroke out to push each head to its correct position with respect to the bead dies in relation to the drum. Stops are used to limit the stroke of the cylinder. When the heads are in correct position other hydraulic cylinders, one in each head, stroke out to expand the bead dies into the drum body. Each cylinder rod carries a cone which pushes the dies to expand or contract same. After the proper stroke is reached and the height of the bead is acquired, the cylinders shift directions and retract the cones. Thus, although there are some mechanical parts the formation of the beads is primarily hydraulic as contrasted with the previous machine No. 812 which is primarily mechanical.
The hydraulic machines such as the No. 203 are easier to adjust for changes in bead height and bead center than the mechanical machines such as No. 812 because the movement of the head and the expanding mechanism are separate. However, a mechanical machine because of its mechanical drive system can be cycled at a higher speed than a hydraulic machine and a mechanical drive produces a known controlled motion whereas a hydraulic machine relies on a cylinder that often can be erratic in its motion but there is a lot of shock in the mechanical systems. Also, in the hydraulic machines the motion is dependent upon too many variables such as pressure, temperature of hydraulic fluid and length of stroke needed. The present machine combines and utilizes the advantage of the mechanical drive of a mechanical machine with the independence of head movement and expansion of the hydraulic machine timed and synchronized electrically by means of limit switches (LS). An important feature of the new machine arises from a combination of advantages of the use of an independent mechanical drive for stroking the heads in and out of a smooth and controlled motion (sometimes called harmonic motion) providing a smooth and uniform change in acceleration as a head starts from a resting position through a uniform deceleraton to its next resting position. All of this occurs while drive gears are at a constant rpm. The clutch and brake are engaged as the head passes through these areas of near zero speed and because of this the shock loads, found in some prior machines, such as the No. 812 or the No. 203, are eliminated. Thus, the present machine may be lighter with potentially a longer life through the elimination of some of the heavy shock forces. This feature alone makes the present machine a substantial improvement over the previous machines.